Microstructure evolution

Coordinated by Pär Olsson, KTH (SE) and Cornelia Heintze, HZDR (DE)

Domain 1 includes the modelling and experimental activities addressing the study of the formation and evolution of irradiation induced nano- and microstructure, as well as microchemical changes leading to a redistribution of alloying elements (Cr and C being in the focus). This domain features a strong component of innovative model development, by addressing the effects of magnetism and finite temperatures on the diffusion properties of the defects that drive the nanostructural evolution, foreseeing also both irradiation and postirradiation experiments using neutrons, self-ions and protons. The ion and proton irradiation conditions for the campaigns to be executed in M4F were already preliminarily defined within the framework of EERA JPNM pilot projects, in order to be comparable with or complementary to neutron irradiation conditions already achieved within the MATISSE project. The neutron-irradiated specimens will be provided as an in-kind contribution to the M4F project.

This domain is divided in two Work Packages

• WP2: Radiation-induced microstructure evolution, devoted to investigating how specific features of FeCrC alloys - model alloys for ferritic/martensitic (F/M) steels - influence and determine the microstructural changes induced in them by neutron irradiation, with a view to identifying the features that mainly cause low temperature hardening and subsequent embrittlement in F/M steels. This will be done by the development of advanced physical models to be combined with refined microstructural examination of irradiated materials
• WP3: Transferability of ion and neutron irradiation. The aim here is to put the use of ion irradiation as a neutron irradiation surrogate and screening tool for the development and qualification of innovative materials for irradiation environments on a more rational basis. This will imply developing suitable microstructure evolution models that explicitly take into account the specificities of ion irradiation, to be used to interpret correctly experimental results and, more importantly, guide their preparation and design. It will also require performing ad hoc ion irradiation campaigns, targeted to verifying specific hypotheses and validating the models



Read recent progresses


In the period between Months 18 and 36

• A huge database of DFT simulations of defect interactions and kinetic properties in the Fe-Cr systems has been generated and analyzed. Publication of the analysis is underway. Several studies on magnetic effects in the Fe-Cr system have been published regarding phase transitions and spin dynamics. Machine learning potentials for radiation effects have been generated and novel fitting and classification methods have been published. This work is partly summarized in deliverable D2.1.
• Object kinetic Monte Carlo (OKMC) models have been developed to study minor solute effects as well as for concentrated Fe-Cr alloys, resulting in two completed publications and one manuscript.
• The ion irradiation campaign for WP2 has been successfully concluded.
• Post-irradiation examination (PIE) of ion- and neutron irradiated Fe-Cr is ongoing and there is active work on connecting the model development to the experimental observations.
• Primary knock-on atom spectra for protons and ions have been generated systematically in order to have a baseline for modeling the experiments carried out in the project. Deliverable D3.1 details all this.
• A code and method comparison study has been completed for teh use of OKMC. In the project there are three different codes under development and in use and they have been benchmarked and compared. The codes have differents strengths and are thus applicable for use to model different aspects of microstructure evolution.
• All ion irradiations for WP3 have been successfully executed during this period. Special focus and efforts have been directed at eliminating and understanding carbon contamination and different irradiation conditions and strategies.
• PIE using transmission electron microscopy (TEM) and atom probe tomography (APT) has been performed and will continue. Preliminary results show what the effects are of the irradiation conditions and strategies.